/**

Write a function:

class Solution { public int solution(int[] A); }

that, given a non-empty zero-indexed array A of N integers, returns the minimal positive integer that does not occur in A.

For example, given:

A[0] = 1

A[1] = 3

A[2] = 6

A[3] = 4

A[4] = 1

A[5] = 2

the function should return 5.

Assume that:

N is an integer within the range [1..100,000];

each element of array A is an integer within the range [−2,147,483,648..2,147,483,647].

Complexity:

expected worst-case time complexity is O(N);

expected worst-case space complexity is O(N), beyond input storage (not counting the storage required for input arguments).

Elements of input arrays can be modified.

*/

import java.util.HashSet;

public class Solution {

public static int solution(int[] array) {

int num = 1;

HashSet<Integer> hashSet = new HashSet<Integer>();

for (int i = 0 ; i < array.length; i++) {

hashSet.add(array[i]);

while (hashSet.contains(num)) {

num++;

}

}

return num;

}

public static void main(String[] args){

int[] array = {1,2,-1,6,7,8};

System.out.println(solution(array));

}

}